1. Field of the Invention
This invention relates generally to chip carriers for high-density integrated circuits (ICs). In particular, it is directed to metallized chip carriers fabricated from wafer-shaped substrates.
2. Description of Related Art
As integrated circuits become more dense, often containing hundreds of I/O connections, prior art techniques of packaging become less suitable. Packaging is considered by many in the industry to be the pacing technology for integrated circuit development. Many designers have recognized the need for developing new techniques for defining high-resolution traces on chip carriers. Up until the present invention, however, creating the required high-resolution traces presented significant manufacturing problems.
In the prior art, chip carriers are fabricated using substrates onto which metallized traces are placed to provide electrical connections from the periphery of the substrate to the integrated circuit packaged within. These traces are typically manufactured using thick-film technology. The need to provide increasing numbers of connections has resulted in thin-film technology being used as a partial solution to bring the traces from the integrated circuit to pins on the carrier. Prior art thin-film technology brings traces from the IC to vias within the carrier, and the vias provide connections to the pins. A primary shortcoming in the prior art is that thin-film technology can not be reliably used to bring the traces from the IC within the carrier to the periphery of the carrier.
Thus, there is a need in the art for high-density interconnects on chip carriers, which can provide traces directly from the integrated circuit packaged within the carrier to the periphery of the carrier, fabricated entirely with thin-film techniques. This shortcoming of the prior art requires that vias be used to connect trace to pin connections, making the overall footprint of the carrier larger than desirable. There is also a need in the prior art to manufacture chip carriers in quantity using thin-film technology, such that a high yield rate is attained with traces as narrow as 5 mils or less.